Hi Andy,

Thanks for your review.

I have published a new revision that addresses the nits.

Regarding your general comment about “capacity planning in TILFA environments”, 
I don’t think it’s necessary to go beyond what the draft is already detailing 
for the following reason:
TILFA is not a traffic-engineering that is fully solving congestion issues 
during FRR. It helps compared to existing LFA/rLFA as it s driving traffic onto 
the “expected” post-convergence path which should be well sized (this avoids 
configuring local policies). It also provides 100% coverage compared to 
LFA/rLFA. However, there could still be situations where congestion could 
occur: PLR uses post-convergence from its point of view (not end-to-end) and 
considering a particular failure type: the failure that occurs could be 
different (link failure while protecting against node, or srlg failure while 
protecting against node).

Brgds,

Stephane


From: Andy Smith <[email protected]>
Sent: jeudi 20 avril 2023 16:23
To: Luc André Burdet <[email protected]>; Yingzhen Qu 
<[email protected]>; [email protected]; 
[email protected]
Subject: Review of draft-ietf-rtgwg-segment-routing-ti-lfa-09

Hello

I have been selected to do a routing directorate “early” review of this draft.

https://datatracker.ietf.org/doc/html/draft-ietf-rtgwg-segment-routing-ti-lfa

The routing directorate will, on request from the working group chair, perform 
an “early” review of a draft before it is submitted for publication to the 
IESG. The early review can be performed at any time during the draft’s lifetime 
as a working group document. The purpose of the early review depends on the 
stage that the document has reached. As this document is in working group last 
call, my focus for the review was to determine whether the document is ready to 
be published. Please consider my comments along with the other working group 
last call comments.

For more information about the Routing Directorate, please see 
http://trac.tools.ietf.org/area/rtg/trac/wiki/RtgDir

Document: draft-ietf-rtgwg-segment-routing-ti-lfa-09
Reviewer: Andy Smith
Review Date: 20 April 2023
Intended Status: Standards Track

Summary:

Thank you for writing this document.

This document is well written. I think that it is ready to be published, but 
there are a few points below that I would like to discuss for clarification. I 
also spotted a few nits that should be fixed at some point before publication.

Comments and Questions:

I would like to see some more detailed examples of capacity planning in TI-LFA 
environments.   The document touches on this to some degree, but a few 
illustrations showing how to accommodate some topological scenarios - 'valley 
free' routing, dissimilar interface speeds, cases where ECMP isn't always 
feasible, etc would be helpful.   Some topological case studies and the effect 
TI-LFA has on the network would be helpful to the operator when designing the 
network.

Nits:

 - Avoid gratuitous promotional language (weasel words) like "Thanks to SR" --> 
not necessary

 - "it looks interesting to steer the traffic onto the post-convergence path" 
--> poor english

 - "w.r.t." --> this is used throughout the document, expand it to 'with regard 
to' or rework the sentence

 - "used by the repair path is recored" --> spelling error

 - Rework this sentence:

   "1 SID repair paths are sufficient to protect more than 99% of the prefix in 
almost all cases"

   should read:

   "1 SID repair path is sufficient to protect more than 99% of the prefixes in 
almost all cases"

 - "only 1 SID is needed to guarantee loop-freeness" --> Awkward use, is 
'freeness' a word?



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